Method to increase the quantity of dissolved gas in a liquid and to maintain the increased quantity of dissolved gas in the liquid until utilized

ABSTRACT

A method for increasing the quantity of a gas, e.g., ozone, dissolved in a liquid, e.g., ultrapure deionized water, are provided. The gas to be dissolved is introduced to the liquid under pressure and the resulting admixture delivered to the end-use station under pressure. Once at the end-use station, the admixture including the liquid and dissolved gas is subjected to controlled dispensing to maintain a high concentration of gas in the dispensed admixture.

REFERENCE TO RELATED APPLICATION

This application is a divisional of application Ser. No. 08/960,277,filed Oct. 29, 1997, now U.S. Pat. No. 5,971,368, and which is herebyincorporated by reference in its entirety.

FIELD OF THE INVENTION

This invention relates to a method and system for increasing thequantity of dissolved gas in a liquid and maintaining a substantialamount of the increased quantity of dissolved gas in solution until thegas/liquid solution is delivered to a point of use. More particularly,the invention relates to a method and system of increasing the quantityof dissolved gas in a liquid by using pressurized mixing and delivery ofthe gas and the liquid. Furthermore, by subjecting the gas/liquidsolution to controlled dispensing at a point of use, a substantialquantity of the increased quantity of gas is maintained in solution.

BACKGROUND OF THE INVENTION

Ozone has long been recognized as a useful chemical commodity valuedparticularly for its outstanding oxidative activity. In fact, ozone isthe fourth strongest oxidizing chemical known, having an oxidationpotential of 2.07 volts. Because of this property, ozone and/or fluidmixtures including ozone are capable of removing a wide variety ofcontaminants, such as cyanides, phenols, iron, manganese, anddetergents, from surfaces. Also, ozone and/or fluid mixtures includingozone are capable of oxidizing surfaces. In particular, ozonated wateris used to “clean”, i.e., oxidize, the surface of silicon wafersin-process in the semiconductor industry. Additionally, ozone is alsouseful for inhibiting, reducing and/or eliminating the accumulation ofbiomass, mold, mildew, algae, fungi, bacterial growth and scale depositsin various aqueous solution systems. When used in this manner, ozonationprovides the advantage of producing a lesser quantity of potentiallyharmful residues than, e.g., chlorination, which leaves undesirablechlorinated residues in aqueous systems.

Because of this wide range of activity, ozone finds application in manydiverse processes. Ozone, for example, has been used as a biocide forthe treatment of drinking water. Additionally, ozone is used forsterilization in the brewing industry, and for odor control purposes inthe sewage treatment industry. Finally, ozonated water finds wideutility in the semiconductor industry, where for example, ozone is usedto clean and surface condition in-process silicon wafers. Additionally,as is described in U.S. Pat. No. 5,378,317, ozonated water is used toremove organic materials, such as photoresist, from the surface ofsilicon wafers. Moreover, ozonated water is used in the semiconductorindustry to form a thin, passivating oxide layer on the surface ofsilicon wafers.

The use of ozonated water provides several advantages in theseapplications. First of all, because ozonated water is generated at thepoint of use, it is free of contaminants, i.e., particles and metals,that are typically present in chemicals that are stored in barrels ordrums. Ozonated water is also less expensive than other oxidizingchemicals and furthermore, since ozonated water naturally decomposes,the use of ozonated water presents no disposal issues. However, theeffectiveness of ozone in each of these applications is adverselyaffected by its low solubility and short-half life (approximately 10minutes) in aqueous solutions. That is, not only is it difficult todissolve ozone in an aqueous solution, but also, once dissolved, it isdifficult to maintain the ozone in solution.

Although several methods of increasing the quantity of dissolved ozonein aqueous solutions are known, each of these prior art methods haslimitations that render them inadequate for certain applications. Forexample, bubbling ozone directly into water at ambient pressure has beenused as a method to dissolve ozone in aqueous solutions. Such atechnique, however, does not optimize the quantity of ozone dissolved,since the ozone bubbles effervesce before a substantial amount of ozonecan be dissolved into solution and/or before the ozonated water can beapplied to the surface to be treated.

Additionally, published European patent application No. EP 0 430 904 A1discloses a process for producing ozonated water comprising the step ofcontacting, within a vessel of defined volume, an ozone-containing gaswith fine droplets of water. However, this process is less than optimalsince it provides limited contact between the ozone-containing gas andwater. That is, as the vessel fills with water, the time of contactbetween the ozone containing gas and the fine water droplets isshortened, resulting in a lesser quantity of ozone being dissolved intosolution. Additionally, this application does not teach a method ofkeeping the ozone in solution until it is delivered to a point of use.Thus, it is possible that, upon delivery, a large quantity of the ozonedissolved in solution will effervesce, and the benefits of the mixingprocess will be lost.

Finally, several methods utilizing cooling to increase the quantity ofdissolved ozone in aqueous solutions have also been proposed. Forexample, U.S. Pat. No. 5,186,841 discloses a method of ozonating watercomprising injecting ozone through an aqueous stream across a pressuredrop of at least 35 psi. The ozonated stream is then combined with asecond stream that is preferably a portion of an aqueous solution whichis recirculating in a cooling water system. The resultant stream isforced to flow at a velocity of 7 feet per second for a distancesufficient to allow 70% of the ozone to be absorbed. Additionally, U.S.Pat. No. 4,172,786 discloses a process for increasing the quantity ofdissolved ozone in an aqueous solution by injecting an ozone containinggas into a side stream conduit which circulates a portion of coolingwater. The ozone-injected water is then mixed with the cooling water ina tower basin, thereby ozonating the water. Finally, U.S. Pat. No.5,464,480 discloses a process for removing organic materials fromsemiconductor wafers using ozonated water. Specifically, this patentteaches that high ozone concentration water, suitable for use in thedisclosed process may be obtained by mixing ozone and water at atemperature of from about 1° C. to 15° C.

Although the systems disclosed in U.S. Pat. Nos. 5,186,841, 4,172,786and 5,464,480 claim to increase the quantity of dissolved ozone inwater, it is more likely that much of the ozone effervesces to theatmosphere and/or is converted to oxygen rather than being dissolved inthe water. Thus, these systems would require the use of a large amountof ozone, which would, in turn, render them costly. Additionally, thesepatents do not disclose methods for optimizing the ozone concentrationat the point of use, and as a result, it is possible that the increasedozone, if any, that is dissolved as a result of cooling the solution,will effervesce out of solution at the point of use.

Thus, there is a need for an efficient method of increasing the quantityof ozone that may be dissolved and maintained in aqueous solution to apoint of use, not only to minimize the amount of ozone used, but also toprovide sufficiently ozonated aqueous solutions for given applications.

SUMMARY OF THE INVENTION

According to the present invention, the above objectives and otherobjectives apparent to those skilled in the art upon reading thisdisclosure are attained by the present invention which is drawn to amethod and system for increasing the quantity of dissolved gas in aliquid and for optimizing the amount of dissolved gas that remains insolution to a point of use. More specifically, it is an object of thepresent invention to provide a method and system for increasing thequantity of dissolved ozone in an aqueous solution, and furthermore, formaintaining the dissolved ozone in solution when delivered to a point ofuse. In this manner, the present invention provides an exceptionallyefficient method and system for producing and using high concentrationozonated water.

Generally, the method involves introducing a stream of a gas to bedissolved into a pressurized vessel wherein the gas is contacted with,and dissolves in, an amount of liquid. Mixing the gas to be dissolvedwith the liquid under pressure results in an increased amount of gasbeing dissolved, relative to the amount of dissolution that occurs atatmospheric pressure. The resulting admixture comprising the liquid andthe dissolved gas is then delivered to a point of use through apressurized conduit, which maintains the increased amount of dissolvedgas in solution.

At the point of use, the admixture is subjected to controlleddispensing. That is, the admixture is dispensed under sufficientlygentle conditions such that the dispensed admixture comprises asupersaturated quantity of dissolved gas at the time the admixturecontacts the substrate. Preferably, the admixture is dispensed underconditions such that the resulting delivered volume of admixture has arelatively small surface area/volume ratio. By virtue of the smallsurface area/volume ratio, the amount of diffusion of the dissolved gasout of the liquid is limited, thus maintaining an increasedconcentration of dissolved gas in the liquid to a point of use. Incontrast, when the surface area/volume ratio is relatively large, thedissolved gas diffuses out of solution more quickly. Thus, dispensemethods which result in delivered volumes of admixture with a largesurface area/volume ratio also result in delivered volumes with adecreased concentration of dissolved gas at the point of use.

Several methods of controlled dispensing are suitable for use in thepresent invention. For example, at the point of use, the admixture maybe subjected to controlled atomization. Specifically, the admixture maybe atomized under conditions such that the average size of the resultingdroplets is large (i.e., the surface area/volume ratio is small)relative to the size of droplets created by conventional atomization.That is, conventional atomization typically produces a fine mist, i.e.,small droplets with a relatively large surface area/volume ratio. Thus,the dissolved gas will diffuse out of solution more quickly resulting ina decreased concentration of dissolved gas at the point of use. Incontrast, the controlled atomization utilized in the method and systemof the present invention results in large droplets with a smallersurface area/volume ratio, thus limiting the amount of diffusion thattakes place and maintaining an increased concentration of dissolved gasin solution to a point of use. Controlled atomization may be effected bya number of mechanisms. For example, in a preferred embodiment, theadmixture may be “gently” impinged with either a second stream ofadmixture or a stream of inert gas, e.g., nitrogen, in a manner thatresults in the desired droplet size.

The controlled dispensing may also be effected by delivering theadmixture through a fan structure at the point of use. When controllablydispensed in this manner, the fan nozzle breaks the stream of admixtureinto smaller sheets or large droplets of admixture, thus resulting indelivered volumes of admixture with the desired small surfacearea/volume ratio.

Yet another example of a controlled dispensing method suitable for usein the present invention includes gently dispensing the admixture as asteady stream. In this embodiment of the invention, the admixture may bedispensed directly to the point of use, e.g., the surface of a siliconwafer, or alternatively, the admixture may be gently dispensed into asuitably sized vessel, i.e., a vessel with a small open surface area,but yet a large volume. That is, the desired small surface area/volumeratio may be achieved simply by gently dispensing the admixture into avessel with suitable dimensions so as to result in the desired surfacearea/volume ratio.

In a preferred embodiment, the liquid utilized in the method and systemof the present invention is a fluorinated liquid, sulfuric acid,hydrochloric acid, hydrofluoric acid, water, ultrapure deionized wateror combinations thereof. More preferably, the liquid utilized is wateror ultrapure deionized water. Additionally, the method and system of thepresent invention are applicable to a variety of cleaning gases,including, but not limited to, hydrogen chloride, nitrogen, carbondioxide, oxygen, hydrogen fluoride, ammonium hydroxide, ozone orcombinations thereof. In a particularly preferred embodiment, the methodand system are used to increase the quantity of dissolved ozone gas inultrapure deionized water.

As a result of the ability of the method and system of the presentinvention to increase and maintain the quantity of dissolved cleaninggas in a liquid, the resulting admixtures are expected to beparticularly useful in the treatment of various surfaces. In particular,ozonated water prepared with the method and/or system of the presentinvention is effective to clean, i.e., oxidize and/or remove organiccontaminants and/or photoresist materials, from surfaces such asin-process silicon wafers. In this regard, the present invention alsoprovides a method for treating surfaces with a cleaning gas.Specifically, the method comprises the steps of preparing an admixturecomprising a cleaning gas dissolved in a liquid within a pressurizedvessel and transferring the admixture to an outlet through a pressurizedconduit. The admixture is then dispensed through the outlet undersufficiently gentle conditions such that the dispensed admixturecomprises a supersaturated quantity of dissolved gas at the time theadmixture contacts the substrate.

The system provided by the present invention generally comprises apressurized vessel and an outlet coupled to the pressurized vesseladapted to dispense a stream of the admixture comprising the liquid andthe dissolved gas under sufficiently gentle conditions such that thedispensed admixture comprises an increased quantity of dissolved gasrelative to admixture produced and dispensed by conventional methods. Inone preferred embodiment, the outlet comprises a spray post comprisingat least one fixed orifice located at a suitable point in a treatmentvessel (e.g., a wet bench) such that admixture may be gently dispensedthereinto. Preferably, the treatment vessel is of dimensions that resultin a small surface area/volume ratio of the dispensed admixture, so thatdiffusion of the gas out of the liquid is minimized. In a secondpreferred embodiment, the outlet comprises a spray post comprising asingle fixed orifice located a suitable distance from a point of usesuch that a steady stream of admixture may be gently dispensedthereonto. In a third embodiment, the spray post may comprise aplurality of one or more sets of fixed orifices distributed along atleast one surface of the spray post at suitable intervals to effect theatomization of a stream of the admixture by impingement with at least asecond fluid stream. The second fluid stream preferably may either be agas stream or a second stream of the admixture. Finally, in a fourthpreferred embodiment, the outlet may comprise a spray post comprising aplurality of fan structures distributed along at least one surface, thefan structures being effective to break up a stream of the admixtureinto sheets and/or large droplets with the desired small surfacearea/volume ratio.

Preferably, the system further comprises a liquid sensing deviceoperatively coupled to the pressurized vessel, a liquid sourceresponsive to the liquid sensing device, a gas source capable ofdelivering a generally continuous supply of gas to the pressurizedvessel, a pressurized liquid outlet conduit fluidly coupled to thepressurized vessel and a pressurized gas outlet conduit through whichundissolved gas can exit the pressurized vessel. Additionally, in apreferred embodiment, the pressurized gas outlet conduit can be used torestrict the flow of undissolved gas out of the pressurized vessel, thusmaintaining pressure in the pressurized vessel and aiding in themotivation of admixture from the pressurized vessel through thepressurized liquid outlet conduit. In a preferred embodiment, thepressurized vessel also comprises an amount of a flow impedimenteffective to increase the residence time of the gas in the pressurizedvessel. For example, the pressurized vessel may comprise packingmaterial, such as a fluorinated polymer, quartz, sapphire orcombinations thereof, or baffles.

As used herein, the term “aqueous” means any fluid admixture thatcontains water as a solvent, including impure water. The term“supersaturated” is meant to indicate that a liquid contains a greateramount of a dissolved constituent than is present in a saturatedsolution of the same components at the same temperature and pressure. Asused herein, the term “ozonated” means that ozone is dissolved in agiven liquid. The phrase “ultrapure deionized water”, as used herein, ismeant to indicate water that has been treated by filtering, reverseosmosis, and UV sterilization so as to remove particles, metals andorganics, respectively. The phrase “controlled dispensing” or“controllably dispensed” is meant to indicate a method of dispensingadmixture under sufficiently gentle conditions such that the dispensedadmixture comprises a supersaturated quantity of dissolved gas at thetime the admixture contacts a substrate. Preferably, the phrase“controlled dispensing” or “controllably dispensed” is meant to indicatea method of dispensing that results in a delivered volume of admixtureof a sufficiently small surface area/volume ratio so that the increasedquantity of dissolved gas is maintained in solution until delivery to apoint of use. The phrase “generally continuous supply” as applied to agas source is meant to indicate a gas source capable of generating a gasfrom suitable precursors or a gas source such as tanks, cylinders, andthe like, for use in a steady state process as opposed to a batchwiseprocess. Finally, the phrase a “continuous process” refers to a processthat can be operated by supplying input materials and withdrawing outputmaterials under substantially steady state conditions after start-up andprior to shutdown.

BRIEF DESCRIPTION OF THE FIGURES

The above mentioned and other advantages of the present invention, andthe manner of attaining them, will become more apparent and theinvention itself will be better understood by reference to the followingdescription of the embodiments of the invention taken in conjunctionwith the accompanying drawing, wherein:

FIG. 1 is a diagram of one representative system capable of producingthe liquid comprising a dissolved gas in accordance with the presentinvention.

FIG. 2 is a side view of a spray nozzle suitable for use as the outletin the system illustrated in FIG. 1.

FIG. 3 is an enlarged cross-sectional view taken along line A—A of FIG.2.

FIG. 4 is a diagram of a representative controlled dispensing systemsuitable for attachment to the outlet in the system illustrated in FIG.1.

FIG. 5 is a graphical depiction of the effect of ozone concentration onthe oxide thickness generated on the surface of a silicon wafer atdifferent time intervals.

DETAILED DESCRIPTION OF THE INVENTION

The embodiments of the present invention described below are notintended to be exhaustive or to limit the invention to the precise formsdisclosed in the following detailed description. Rather the embodimentsare chosen and described so that others skilled in the art mayappreciate and understand the principles and practices of the presentinvention.

The present invention represents an improvement in producing liquidscomprising a dissolved gas. Applicants have discovered that, byintroducing a gas into a pressurized vessel containing a liquid;delivering the resulting admixture to a point of use through apressurized conduit; and subjecting the admixture to controlleddispensing at the point of use, the quantity of dissolved gas in theliquid is not only enhanced over the quantity of dissolved gas in theliquid at atmospheric pressure, but also, that a substantial portion ofthe enhanced amount of dissolved gas stays in solution to the point ofuse.

Referring now to FIG. 1, there is illustrated a system (1) embodying theprinciples of the present invention. System (1), as illustrated, isadapted for the production of ozonated water, however, the principles ofthe present invention are applicable to any liquid/gas solution. System(1) generally comprises a pressurized vessel (2) having an internalvolume (30) within which a body of liquid (31) is contacted with a gas(32). Gas (32) is dissolved in liquid (31) as a result of such contact.Liquid (31) is supplied to pressurized vessel (2) through liquid inletport (33) at the top of pressurized vessel (2), and gas (32) enters thepressurized vessel (2) through bubbler (34) positioned at the bottom ofpressurized vessel (2). Thus, gas (32) percolates upward throughpressurized vessel (2) while liquid (31) generally flows downward. Suchcounterflow of gas (32) and liquid (31) provides a relatively longperiod of contact between gas (32) and liquid (31), thereby facilitatingthe dissolution of gas (32) in liquid (31).

To further increase the period of contact between gas (32) and liquid(31), the internal volume (30) of pressurized vessel (2) may include aconventional flow impediment (not illustrated). That is, the internalvolume (30) of pressurized vessel (2) may contain an amount of packingmaterial and/or baffles sufficient to provide an increased period ofcontact between gas (32) and liquid (31). Examples of packing materialssuitable for use in the present invention include, but are not limitedto, quartz, sapphire, fluorinated polymers or combinations thereof. Forexample, depending upon pressure, gas (32) may flow through a vessel (2)that is 1 meter high in approximately 2 seconds. However, in a vessel(2) of the same height, flow impediments can increase this residencetime by at least a factor of two. That is, a vessel (2) that is 1 meterhigh and packed with flow impediment will have a residence time of fromabout 5 to 10 seconds.

Applicants' invention is based, at least partially, on Henry's Law,which states that all other things being constant, as the pressure atthe interface between a liquid and a gas increases, the quantity of gasin the liquid increases. In other words, greater quantities of gas canbe dissolved in pressurized liquids than can be dissolved in the sameliquids at lower pressures. While higher pressures within thepressurized vessel (2) will result in an increased quantity of ozonebeing dissolved into solution, the pressure of pressurized vessel (2) isgenerally constrained by the safety considerations involved in operatinga manufacturing process in which hazardous chemicals may be involved. Itis therefore preferred that the pressure in the pressurized vessel (2)be maintained at a level of from about 1.1 to about 10 atmospheres. Morepreferably, the pressure of pressurized vessel (2) is maintained at alevel of from about 2 to about 5 atmospheres. Most preferably, thepressure of pressurized vessel (2) is from about 2 to about 3atmospheres.

The method and system of the present invention may be easily adapted toaccommodate liquids and/or gases that are corrosive. Thus, given thatozonated water is corrosive, pressurized vessel (2) and any flowimpediment included in the internal volume (30) of pressurized vessel(2) are preferably constructed of a material, such aspolytetraflouroethylene (commercially available under the tradedesignation Teflon® PTFE from E.I. DuPont deNemours & Co., Wilmington,Del.) resistant to the deteriorating effects of corrosive chemicals.

Pressurized vessel (2) is connected to liquid source (4) by liquidconduit (35) for supplying the desired liquid to the pressurized vessel(2). In a preferred embodiment, liquid source (4) supplies ultrapuredeionized water through liquid conduit (35) to pressurized vessel (2).Optionally, liquid conduit (35), may comprise liquid pressure regulator(20) and liquid pressure gauge (21) to control the pressure of liquid(31) flowing to pressurized vessel (2). Flow from liquid source (4) intopressurized vessel (2) is further preferably controlled by liquid valve(22) that is responsive to liquid sensing device (3). Liquid sensingdevice (3) is positioned on pressurized vessel (2) such that liquidsensing device (3) is capable of detecting an amount of liquid (31) inthe pressurized vessel (2). In this manner, the transport of the liquidfrom the liquid source (4) to the pressurized vessel (2) may becontrolled in response to a signal from the liquid sensing device (3).

The rate of flow of liquid from the liquid source (4) to the pressurizedvessel (2) is not critical to the practice of the present invention andmay be set at any convenient level. Generally speaking, the rate ofliquid flow may range from 1 liter/minute to 25 liters/minute.Additionally, although FIG. 1 shows a preferred configuration in whichthe liquid source (4) is connected to the pressurized vessel (2) at thetop of the pressurized vessel (2), the liquid source (4) may beconnected to the pressurized vessel (2) at any other desired location ormultiple locations. However, connection at the top of pressurized vessel(2) is generally preferred as such connection facilitates thecounterflow contact between gas (32) and liquid (31).

It is further preferred that a pressure differential exist betweenliquid source (4) and pressurized vessel (2) to ensure that the flow ofliquid (31) is maintained in the desired direction, i.e., intopressurized vessel (2). However, a large pressure differential is notrequired. It is sufficient, for example, if pressurized vessel (2) is at2.5 atmospheres, that the liquid (31) flowing from liquid source (4) isat a pressure of 2.6 atmospheres. It is additionally preferred that apressure differential exist between gas source (10) and pressurizedvessel (2) to ensure that the flow of gas (32) is maintained in thedesired direction, i.e., into the pressurized vessel (2). Again, a largepressure differential is not required, that is, it is sufficient ifpressurized vessel (2) is at 2.5 atmospheres, that gas (32) flowing fromgas source (10) is at a pressure of 2.6 atmospheres.

Ozone is supplied to pressurized vessel (2) through pressurized gasconduit (18). Since ozone has a relatively short half life, it ispreferred that it be supplied on demand from, e.g., ozone gas generator(5). However, any ozone source capable of maintaining a generallycontinuous flow of ozone may be used. In the embodiment shown, the ozonegas generator (5) is of the type that uses electricity to generate ozonefrom oxygen. Oxygen is supplied from an oxygen gas facility (10) toozone gas generator (5) through conduit (36). Conduit (36) comprises aprecursor supply pressure regulator (15), a precursor supply pressuregauge (11), a precursor supply 2-way valve (12) and a precursor supplymass flow controller (13). These fixtures are included to control theflow rate of oxygen, however, neither the fixtures nor theirconfiguration are considered critical to the practice of the presentinvention. Cooling media (14), preferably water, is supplied to theozone gas generator (5) through a cooling media valve (16). Coolingmedia (14) flows through ozone gas generator (5) and exits throughcooling media drain (38).

The ozone generated from the gas source (5) is supplied to thepressurized vessel (2) through pressurized gas conduit (18). Given thatozone gas is corrosive, pressurized gas conduit (18) is preferablyconstructed of a material resistant to the deteriorating effects ofozone. For example, pressurized gas conduit (18) may be constructed ofstainless steel, quartz, or a fluorinated polymer such as Teflon® PFA orTeflon® PTFE, commercially available from E.I. DuPont deNemours & Co.,Wilmington, Del. Furthermore, since ozone is more corrosive in a wetenvironment, it is preferred that, at some point near the pressurizedvessel (2), such as the point labeled (37) in FIG. 1, where thecollection of moisture is possible, that pressurized gas conduit (18) isconstructed of a material resistant to wet ozone, such as a fluorinatedpolymer (i.e., Teflon® PFA or Teflon® PTFE).

A gas check valve (19) may be provided in pressurized gas conduit (18)to ensure that the flow of the ozone through the system proceeds in onedirection, i.e., towards the pressurized vessel (2). Any type of valvecapable of ensuring unidirectional flow may be used, for example, a balland socket valve is suitable for use as the pressurized gas check valve(19). Additionally, a pressurized gas 2-way valve (20) may be providedin pressurized gas conduit (18) as another method of controlling theflow of the ozone from the ozone gas generator (5). Finally, pressurizedgas conduit (18) may further comprise a gas filter (21) suitable forremoving particulates from the ozone gas. Any type of filter may beused, the only requirement being that the filter material must beresistant to ozone. Examples of filters suitable for use in the systemof the present invention include hydrophobic membrane filters, such asthose commercially available from Pall Ultrafine Filtration Company,East Hills, N.Y.

Although FIG. 1 shows a preferred configuration in which pressurized gasconduit (18) is attached to the pressurized vessel (2) at the bottom ofthe vessel, pressurized gas conduit (18) may be attached to pressurizedvessel (2) in any other desired location(s). However, it is generallypreferable that pressurized gas conduit (18) be attached at the bottomof pressurized vessel (2) so as to maximize the counterflow contact ofliquid (31) and gas (32). Additionally, as illustrated in FIG. 1, theozone gas is preferably bubbled into the pressurized vessel (2). Thatis, the ozone gas stream may be directed through a bubbler (34).However, although bubbling the ozone into pressurized vessel (2) ispreferred, the ozone may be introduced into the pressurized vessel (2)in a variety of manners, e.g., as a steady stream, such as through afrit made of an ozone resistant material, such as quartz or sapphire.

In addition to the two inlet conduits to the pressurized vessel (2)(i.e., the liquid conduit (35) and the pressurized gas conduit (18)),there are preferably two outlet conduits positioned on the pressurizedvessel (2). Specifically, there is preferably positioned on thepressurized vessel (2) a pressurized gas outlet conduit (39) and apressurized liquid outlet conduit (6).

Pressurized gas outlet conduit (39) is coupled to the pressurized vessel(2) such that undissolved gas can be withdrawn from the pressurizedvessel (2). Pressurized gas outlet conduit (39) preferably comprises gasback pressure regulator (7), so that pressure within the pressurizedvessel (2) is maintained within the desirable ranges described above.Optionally, the pressurized gas outlet conduit (39) may comprise a gaspressure gauge (23), an exhaust system (25) comprising an ozone catalystwhich converts ozone to oxygen and thus ensures that no ozone gasescapes the system, and a gas filter (24) to prevent the back flow ofcontaminants from the exhaust system (25). These fixtures, althoughdesirable, are not critical to the practice of the present invention.

The second outlet conduit positioned on pressurized vessel (2) ispreferably a pressurized liquid outlet conduit (6) positioned such thatan amount of the liquid comprising an amount of dissolved gas can bewithdrawn from the pressurized vessel (2). As is illustrated in FIG. 1,liquid/gas admixture is dispensed from the pressurized liquid outletconduit (6) preferably through outlet (40), which may preferablycomprise one or more fixed orifices, said orifices being of a sizeeffective to maintain a desired amount of pressure of theliquid/dissolved gas admixture in the pressurized liquid outlet conduit(6) until the liquid is dispensed through outlet (40). In a preferredembodiment, the outlet (40) comprises a spray post with a plurality offixed orifices dispersed along at least one surface at suitableintervals to accomplish the desired dispensing and surface treatment.The shape of the orifices is not critical to the practice of the presentinvention and thus the orifice may be square, rectangular, elliptical orcircular. In a preferred embodiment, the outlet (40) comprises aplurality of fixed orifices that are circular and are of diameter fromabout 0.02 to 0.05 inches (i.e., from about 0.51 to 1.27 mm) indiameter.

The configuration of pressurized gas outlet (39) helps motivateadmixture from pressurized vessel (2) through pressurized liquid outletconduit (6). Specifically, the flow of undissolved gas exhausted throughpressurized gas outlet conduit (39) is restricted sufficiently tomaintain a back pressure with respect to pressurized vessel (2). Thisback pressure helps push admixture out of pressurized vessel (2) throughpressurized liquid outlet conduit (6). As is shown, back pressureregulator (7) is used to restrict gas flow through pressurized gasoutlet conduit (39), but any other kind of suitable flow restrictioncomponentry could be used as desired. With the development of this backpressure, mechanical pumps are not required to transport admixture frompressurized vessel (2) to a point of use, thus reducing the cost andcomplexity of system (1).

Additionally, the flow of gas through pressurized gas outlet conduit(39) may be adjusted to help regulate the flow rate of admixture throughpressurized liquid outlet conduit (6). For example, as the flow of gasthrough pressurized gas outlet conduit (39) is restricted, back pressurein pressurized vessel (2) increases as does the motivating force againstthe admixture. Accordingly, the greater the flow restriction that isestablished through pressurized gas outlet conduit (39), the greater theflow rate of admixture will be through pressurized liquid outlet conduit(6). Conversely, the lesser the flow restriction through pressurized gasoutlet conduit (39), the lesser the flow rate of admixture will bethrough pressurized liquid outlet conduit (6).

The pressurized liquid outlet conduit (6) may further comprise a liquiddrain line (26) through which a relatively minor flow of admixture canbe drawn so that system (1) can be continuously operated, even absentdemand for admixture from outlet (40). Additionally, drain line (26)provides a convenient location to place an ozone concentration sensor(27), by which the ozone concentration of the admixture can bemonitored.

The flow rate through drain line (26) is preferably maintained at such arate that system (1) may be kept operational, but at a low enough rateso that excessive amounts of water and ozone are not wasted. Forexample, for a system in which ozone flow into pressurized vessel (2) is1.0 to 25.0 l/min, flow through drain line (26) is suitably establishedat 0.2 to 1.0 l/min. Preferably, flow through drain line (26) willremain constant at from about 0.4 l/m to about 0.6 l/m. Furthermore, inaddition to concentration sensor (27), drain line (26) comprises a fixedorifice (28) for limiting the flow of ozonated water through the ozoneconcentration sensor (27). Additionally, if drain line (26) is to beemployed, it is preferred that drain (29) be included on drain line(26).

Referring now to FIGS. 2 and 3, there is illustrated a side view of apreferred embodiment of a spray post (200) suitable for use as outlet(40) as illustrated in FIG. 1 of the present invention. Generally, spraypost (200) is configured to controllably atomize a stream of ozonatedwater under conditions such that relatively large droplets of the streamare formed and then allowed to contact with the surface to be treated.By subjecting the stream of ozonated water to controlled atomization inthis way, a greater quantity of ozone remains in solution for moreeffective treatment of the surface. That is, the droplets created bycontrolled atomization would be supersaturated with ozone.

Spray post (200) is capable of achieving such atomization by relyingupon the principles of stream impingement to gently atomize a stream ofthe ozonated water. More specifically, a stream of the ozonated waterand one or more other streams (which can be another stream of ozonatedwater, a stream of a nonreactive gas, such as N₂ and/or some otherfluid), can be impinged against each other under conditions such thatthe relatively large droplets are formed.

Spray post (200) is additionally capable of achieving a controlleddispensing of ozonated water by virtue of the utilization of a pluralityof fan mechanisms. That is, the fan mechanisms would operate to break astream of the ozonated water into sheets and/or relatively largedroplets to be distributed onto the surface to be treated. Finally,spray post (200) is capable of controllably dispensing ozonated water asa steady stream, i.e., a stream of ozonated water may be caused to flowthrough one orifice (240) of a triad of orifices (240) without beingimpinged with another stream of fluid.

As illustrated, spray post (200) comprises mounting flange (210) andnozzle (220). Mounting flange (210) is adapted to be coupled to system(1) as illustrated in FIG. 1. Mounting flange (210) comprises admixtureinlet (212) for receiving ozonated water produced by the system of thepresent invention, while gas inlet (214) is adapted to receive anatomizing gas from a suitable source. In preferred embodiments, theatomizing gas is an inert gas, such as nitrogen. Additionally, mountingflange (210) comprises nut (216) for attaching mounting flange (210) toa lid (218) (shown in part) of a vessel that would contain the items tobe treated with the ozonated water.

Nozzle (220) comprises a plurality of fixed orifices (240) arranged intriads, i.e., sets of three, distributed along the length of nozzle(220). Each triad of orifices is arranged so that streams (at least oneof which is the ozonated water) ejected from two or more of the triadorifices can be caused to impinge each other so as to atomize theozonated water stream(s). That is, the orifices within each triad arepreferably directed toward each other in such a manner that stream(s) ofozonated water ejected from one or more of the orifices will impinge,resulting in the stream(s) being broken up into large droplets.Alternatively, ozonated water may be ejected from one of the triadorifices and not be caused to impinge with a second fluid stream,thereby resulting in the delivery of a steady stream of the admixture.Nozzle (220) further includes a plurality of fans (224) distributedalong the length of nozzle (220). Fans (224), in one embodiment of thesystem of the present invention, are used as an alternative to streamimpingement in order to break a stream of ozonated water into sheets orlarge droplets.

Nozzle (220) further comprises a number of internal longitudinalpassages fluidly coupling atomizing gas inlet (214) and admixture inlet(212) to the plurality of fixed orifices (240). Specifically, there isprovided longitudinal passages (228, 232, and 234) that are fluidlycoupled to fixed orifices (240) by corresponding outlet passages (242,244, and 246) associated with each orifice triad. Similarly,longitudinal passage (230) is fluidly coupled to each fan (224) byvirtue of corresponding outlet passages (238). Thus, for example, fluidtransported through any of longitudinal passages (228, 232, and 234) isconveyed through outlet passages (242, 244 and 246), ejected fromcorresponding fixed orifices (240), and impinged in order to achievecontrolled atomization of ozonated water. In a similar fashion, fluidtransported through longitudinal passage (230) is conveyed throughoutlet passage (238) and dispensed through fans (224), thereby breakingthe stream of ozonated water into sheets or large droplets.

Referring now to FIG. 4 there is illustrated a schematic diagram of awet bench (400) suitable for attachment to outlet (40) as illustrated inFIG. 1 to effect an alternate mode of the controlled dispensing asdescribed herein. As shown, pressurized liquid outlet conduit (6) isfluidly coupled to outlet (40) which is fluidly coupled to vessel (450).Vessel (450) is of a suitable size so as to be capable of enclosing oneor more silicon wafers (460) for cleaning. Vessel (450) is preferablyalso of suitable size such that the desired small surface area/volumeratio will be achieved upon controllably dispensing admixture intovessel (450).

Wafer (460) is supported by carrier (462) in a manner such that at leastone surface of the silicon wafer (460) may be contacted by ozonatedwater introduced to vessel (450) through outlet (40). Vessel (450)preferably also comprises outlet (470) to prevent overflow of ozonatedwater out of vessel (450). Flow of ozonated water through outlet (470)is controlled by valve (472). Ozonated water exiting vessel (450)through outlet (470) may simply be dispensed of, or alternatively may berecirculated back through the system through a recirculation loop (notshown).

In operation, ozonated water will be controllably dispensed into vessel(450) through outlet (40) under sufficiently gentle (i.e. non-turbulent)conditions such that a substantial amount of dissolved ozone remains insolution. Ozonated water will be allowed to flow into vessel (450) untila sufficient amount has entered to cover at least one surface of siliconwafer (460). At this time, valve (472) on outlet (470) may be activatedand the flow of ozonated water through outlet (470) adjusted to beequivalent to the flow into vessel (450) through outlet (40). In thismanner, a continuous method for cleaning the surface of silicon wafersis provided.

Without being bound by any theory, Applicants believe that the abilityto retain such a high percentage of ozone in solution is dependent uponone or more of (a) the surface area/volume ratio of the deliveredadmixture generated by controlled dispensing, (b) the time that elapsesfrom the time the admixture is dispensed from spray post (200) to thetime the atomized admixture reaches the point of use, i.e., the surfacebeing treated; and/or (c) the flow rate of the stream of admixture beingdispensed.

With respect to the surface area/volume ratio, for example, the abilityof the ozone to diffuse out of the dispensed volume of admixture dependsin part upon the surface area of the admixture/atmosphere interface. Fora larger surface area/volume ratios, i.e., smaller droplets or vesselswith a large surface area relative to volume, the ozone has ampleopportunity to diffuse from the surface area of the droplet or thevessel, and thereby be lost. On the other hand, for smaller surfacearea/volume ratios, i.e., larger droplets or vessels with a smallsurface area relative to volume, the ozone is less able to diffuse fromthe surface area of the droplet or the vessel. In practical effect, moreozone is trapped in the larger sized droplets (or vessel with a smallsurface area/volume ratio) and remains available for surface treatment.

Thus, in the practice of the present invention, it is preferred that theadmixture is dispensed under sufficiently gentle conditions in a mannersuch that the resulting volume of dispensed admixture has a smallsurface area/volume ratio. That is, if the admixture is to be atomizedor dispensed by a fan structure, it is preferred that the resultingdroplets have an average diameter of at least 0.5 mm, preferably fromabout 0.5 mm to about 5 mm, more preferably 1 mm to 3 mm. Averagedroplet size may be determined by any suitable manner known by those ofordinary skill in the art. For example, droplet size may be determinedby visual observation of the droplets as illuminated by a strobe light.Alternatively, if the admixture is to be dispensed into a treatmentvessel, as for use in a wet bench method of processing wafers, ordispensed directly to a point of use as a steady stream, it is preferredthat the admixture be dispensed under laminar flow conditions,preferably at a flow rate of from about 1 liter/minute to about 20liters/minute. If the admixture is to be dispensed into a treatmentvessel, it is further preferred that the vessel have a surfacearea/volume ratio of from about 0.01 to about 0.1.

With respect to the time that elapses from the time the admixture isdispensed from spray post (200) to the time that the admixture reachesthe point of use, generally, more ozone can escape from the admixture asthis period of time becomes longer. Accordingly, to further maximize theamount of ozone remaining in the admixture at the point of use, it ispreferred that the distance between the spray post (200) and the surfacebe as close as is practically possible. It is further preferred,therefore, that the time that elapses between the moment the admixtureis dispensed to the moment it reaches the point of use is from about0.01 seconds to about 5 seconds. More preferably, the time that elapseswill be less than 2 seconds.

With respect to the flow rate of the stream being dispensed, it ispreferred that the stream of admixture to be dispensed is supplied tospray post (200) under laminar flow conditions. Generally, ozone candiffuse more easily from admixture delivered as a turbulent stream, sothat transporting stream under laminar flow conditions further maximizesthe amount of ozone that remains in the dispensed admixture.

The present invention will now be further described with reference tothe following examples.

EXAMPLE 1

This experiment was conducted to show the effect of different dispensetechniques on the amount of ozone that remains in an ozonated watersolution at the point of use. The effects on the efficiency of thedispense methods were evaluated when the following parameters werevaried: atomizing gas pressure, nozzle design, and the rate of flow ofadmixture through the nozzle.

The initial ozone concentration was measured by taking a side stream ofozonated water from the pressurized vessel and using a commerciallyavailable sensor to measure the dissolved ozone concentration. A secondsensor was used to measure the dissolved ozone concentration after theliquid was dispensed through the spray post by collecting the liquid andfunneling it to the sensor. The percentage ozone remaining in solutionwas calculated by the formula [O3_(final)]/[O3_(initial)]*100, where thesymbol [O3] stands for the concentration of ozone dissolved in water.

Using the spray post described hereinabove, atomization was achieved bycausing a stream of atomizing gas to impinge with a stream of ozonatedwater. Two sets of controls were employed; one representative ofozonated water delivered as a steady stream (“no atomization”) and onerepresentative of “conventional” atomization (i.e., atomization withatomizing gas supplied at high pressure, specifically, atomization at 20and 40 psi). Experiments were then conducted on ozonated water subjectedto controlled atomization with atomizing gas supplied at 4 psi and 6psi.

Using conventional atomization, droplets of approximately 0.1 mm werecreated. Additionally, and as is illustrated in Table 1, hereinbelow,conventional atomization resulted in the loss of up to 92% of the ozonethat had been in solution before dispensing. In contrast, usingcontrolled atomization, droplets of about 1.0 mm in diameter wereobserved, and 50-61% of the ozone remained in solution. Additionally,the delivery of a steady stream of ozonated water (i.e., through onefixed orifice of the nozzle with no impingement with an atomizing gas)at a flow rate of 1000 cc/min at 22° C. resulted in 67% of the dissolvedozone remaining in solution.

Additional experiments were conducted to evaluate the efficiency ofutilizing the fan mechanisms described hereinabove to controllablydispense the ozonated water. That is, using the spray post describedabove, a stream of ozonated water was caused to flow through the fanstructure described, resulting in the stream of ozonated water beingbroken up into sheets and/or large droplets. As is also shown in Table1, using fans to atomize the ozonated water produced droplets with adiameter of about 1.0 mm and a relatively high percentage of ozoneremaining in solution.

Finally, experiments were conducted to evaluate the efficiency of usingstream impingement of two streams of ozonated water to controllablydispense the ozonated water. That is, utilizing the spray post describedabove, two streams of ozonated water were made to impinge through 8 or75 fixed orifices with diameters of from about 0.022 inches to about0.028 inches. When both streams were at a flow rate of 2.0liters/minute, it was found that up to 48% of the ozone remains insolution. When the two streams of ozonated water are at higher flowrates prior to impingement, an overall smaller droplet diameter wasobserved. As a consequence, a lesser amount of ozone remained insolution. The results of this experiment are also illustrated in Table1, hereinbelow.

TABLE 1 Initial Concentration % O₃ water Conditions conc. afterdispensing remaining pressure 1000 cc/min No atomization, 60 deg C. 8.3ppm 2.1 ppm 25% 20 psi 1000 cc/min, No atomization, 40 deg C. 8.7 ppm5.3 ppm 60% 20 psi 1000 cc/min, No atomization, 22 deg C. 7.9 ppm 5.3ppm 67% 20 psi 1600 cc/min, High atomization (40 psi), 22 deg C. 7.8 ppm0.6 ppm  8% 20 psi 1600 cc/min, Low atomization (20 psi), 22 deg C. 7.5ppm 1.2 ppm 16% 20 psi 1600 cc/min, 6 psi atomization, 22 deg C. 7.6 ppm3.8 ppm 50% 20 psi 1600 cc/min, 4 psi atomization, 22 deg C. 7.8 ppm 4.4ppm 57% 20 psi 1600 cc/min, 4 psi atomization, 22 deg C. 8.0 ppm 4.9 ppm61% 20 psi Fan spray 2.0 1/min, 22 deg C. 8.2 ppm 5.4 ppm 75% 20 psi Fanspray 1.5 1/min. 22 deg C. 8.5 ppm 6.6 ppm 76% 20 psi Fan spray, 1.01/min. 22 deg C. 7.2 ppm 7.0 ppm 82% 20 psi Colliding streams, 75 holes,2 L/min, 22 deg C. 50.0 ppm  24.0 ppm  48% 30 psi Colliding streams, 8holes, 2 L/min, 22 deg C. 50.0 ppm  17.3 ppm  35% 30 psi Collidingstreams, 75 holes, 10 L/min, 22 deg C. 50.0 ppm  7.6 ppm 15% 30 psi

In summary, dispensing the admixture at a high rate of flow (e.g. 1600cc/min) at atomization pressures of 20 psi or greater results in adramatic decrease of ozone that remains in solution. In contrast, byutilizing a low rate of flow (e.g., 1000 cc/min) and/or a low pressuremeans of atomization, an increased amount of ozone remains dissolved inthe admixture. Additionally, when a fan spray method is used to dispensethe admixture, up to 82% of the dissolved ozone remains in solution.

EXAMPLE 2

This experiment was conducted to show the effect of increased ozoneconcentration on the oxidation of a silicon surface. In this experiment,the dispense technique and all other parameters were held constant,while the pressure of the pressurized vessel was varied. As a result ofthe varied pressure, the concentration of dissolved ozone in watervaried, and thus the time required for complete oxidation of a siliconsurface.

Specifically, 1.0 ppm ozonated water was generated at a low powersetting on the ozone gas generator and by maintaining the pressurizedvessel at 0 psi, 10.0 ppm ozonated water was generated at a high powersetting on the ozone gas generator and by maintaining the pressurizedvessel at 0 psi; and 50.0 ppm ozonated water was generated using a highpower setting on the ozone gas generator and maintaining the pressurizedvessel at a pressure of 25 psi. The ozonated water was then dispensedonto silicon wafer surface.

As is illustrated in FIG. 5, 10 minutes was required to completelyoxidize the surface of a wafer using 10.0 ppm ozonated water. Incontrast, the 50.0 ppm ozonated water completely oxidized the surface ofthe silicon wafer is 2 minutes. It was thus concluded that a five-foldincrease in ozone concentration results in a five-fold decrease in thetime necessary to completely oxidize a silicon wafer surface.

Other embodiments of this invention will be apparent to those skilled inthe art upon consideration of this specification or from practice of theinvention disclosed herein. Various omissions, modifications, andchanges to the principles and embodiments described herein may be madeby one skilled in the art without departing from the true scope andspirit of the invention which is indicated by the following claims.

What is claimed is:
 1. A method for treating a surface with ozonecomprising the steps of: preparing an admixture comprising ozonedissolved in a liquid within a pressurized vessel; and controllablyapplying the admixture from the pressurized vessel trough an outlet tothe surface under sufficiently gentle conditions that the appliedadmixture comprises a supersaturated quantity of ozone at and during thetime the applied admixture contacts the surface.
 2. The method of claim1, wherein said liquid is selected from water, ultrapure deionizedwater, sulfuric acid, hydrochloric acid, hydrofluoric acid, afluorinated liquid or combinations thereof.
 3. The method of claim 2,wherein said liquid comprises water or ultrapure deionized water.
 4. Themethod of claim 1, wherein the applying step comprises impinging astream of the admixture with a second fluid stream under conditionseffective to provide atomized droplets comprising a supersaturatedquantity of ozone at the time the droplets contact the substrate.
 5. Themethod of claim 4, wherein the second fluid stream is a gas stream at apressure in the range of from about 1 psi to about 10 psi.
 6. The methodof claim 4, wherein the second fluid stream comprises a second stream ofthe admixture.
 7. The method of claim 1, wherein the applying stepcomprises delivering a steady stream of the admixture to a point of use.8. The method of claim 1, wherein the surface is a surface of anin-process silicon wafer.
 9. The method of claim 8, wherein the surfacecomprises a photoresist material.
 10. The method of claim 8, wherein thesurface comprises an organic contaminant.
 11. The method of claim 1,wherein the step of preparing said pressurized admixture comprises:transporting a supply of the ozone to the pressurized vessel; and whilethe ozone is within the pressurized vessel, contacting the ozone with anamount of the liquid such that an amount of ozone is dissolved in saidliquid.
 12. The method of claim 11, further comprising the step oftransporting the liquid from a liquid source into said pressurizedvessel, said pressurized vessel comprising a liquid sensing devicepositioned on the pressurized vessel such that the liquid sensing deviceis capable of detecting an amount of liquid in the pressurized vesseland said liquid source being responsive to said liquid sensing devicesuch that the transport of the liquid from the liquid source to thepressurized vessel can be controlled in response to a signal from saidliquid sensing device.
 13. The method of claim 1, wherein saidpressurized vessel is at a pressure of from about 1.1 atmospheres toabout 10 atmospheres.
 14. The method of claim 1, wherein the liquid isselected from water, ultrapure deionized water, sulfuric acid,hydrochloric acid, hydrofluoric acid, a fluorinated liquid or acombination thereof, and wherein the surface comprises a materialselected from a photoresist material, an organic contaminant, or acombination thereof.
 15. The method of claim 1 wherein the surface isthe wafer surface of an in-process semiconductor wafer.
 16. The methodof claim 4, wherein the droplets have an average diameter of at leastabout 0.5 mm.
 17. The method of claim 16 wherein the droplets have anaverage diameter of about 0.5 mm to about 5 mm.
 18. The method of claim16 wherein the droplets have an average diameter of about 1 mm to about3 mm.
 19. The method of claim 16 wherein the time that elapses betweenthe moment the admixture is dispensed to the moment it reaches thesubstrate is from about 0.01 seconds to about 5 seconds.
 20. The methodof claim 16 wherein the time that elapses between the moment theadmixture is dispensed to the moment it reaches the substrate is lessthan 2 seconds.
 21. The method of claim 1 wherein the applying stepcomprises dispensing the admixture by a fan structure under conditionseffective to provide droplets comprising a supersaturated quantity ofozone at the time the droplets contact the substrate.
 22. The method ofclaim 16 wherein the substrate is the wafer surface of an in-processsemiconductor wafer.
 23. The method of claim 1, wherein the admixture isapplied onto the substrate as a steady stream under laminar flowconditions at a flow rate of about 1 liter/minute to about 20liters/minute.
 24. The method of claim 23 wherein the substrate is thewafer surface of an in-process semiconductor wafer.
 25. The method ofclaim 1, wherein the admixture is applied to the substrate bywithdrawing a supply of an admixture comprising the liquid and dissolvedozone from the pressurized vessel into a treatment vessel having asurface area/volume ratio of from about 0.01 to about 0.1.
 26. Themethod of claim 25 wherein the substrate is the wafer surface of anin-process semiconductor wafer.
 27. A method for treating a surface ofan in-process semiconductor wafer comprising the steps of: providing thein-process semiconductor wafer within a wafer environment having a firstgas pressure; providing a pressure vessel; providing a liquid; providingozone for treating the wafer surface, the ozone having a solubility inthe liquid such that the ozone has a first equilibrium concentrationwithin the liquid in a pressure vessel at the first gas pressure;bringing the ozone into contact with the liquid; pressurizing the ozoneand the liquid in the pressure vessel to greater than the first gaspressure creating a treating substance having a second ozoneconcentration higher than the first concentration; and controllablyapplying the treating substance from the pressure vessel onto the wafersurface in a sufficiently gentle manner such that the applied treatingsubstance comprises a concentration of dissolved ozone higher than thefirst equilibrium concentration at and during the time the treatingsubstance contacts the surface.
 28. The method of claim 27, wherein theliquid is selected from the water, ultrapure deionized water, sulfuricacid, hydrochloric acid, hydrofluoric acid, a fluorinated liquid or acombination thereof, and wherein the surface comprises a materialselected from a photoresist material, an organic contaminant, or acombination thereof.
 29. The method of claim 27, the wafer surfacecomprising a material, and the controllably applying step comprisingremoving at least a portion of the material.
 30. The method of claim 27,the wafer surface comprising an oxidizable material, and wherein thecontrollably applying step comprises oxidizing the material.